Adjustable mounting for tuning member



Feb. 27, 1968 G. s. FAY 3,371,303

ADJL'S'I'ABIJE MOUNTING FOR TUNING MEMBER Filed April 22, 196e INVENTOR.Geven@ s. 14/

, frafP/ve'y United States Patent 3,371,303 ADJUSTABLE MOUNTING FORTUNING MEMBER Gerald S. Fay, Springfield, Mass., assignor to GeneralInstrument Corporation, a corporation of Delaware Filed Apr. 22, 1966,Ser. No. 544,421 19 Claims. (Cl. 336-130) The present invention relatesto an improved construction for mounting a tuning member in a mannersuch that it may readily have its position adjusted, and will thenreliably remain in that position.

In many communication system tuning devices a movable part carries atuning member such as a ferromagnetic core, and moves it relative to aiixedly mounted tuned member, thereby to vary the electrical characterof the tuned member and produce the desired tuning effect. In soi-calledgang tuning, where a plurality of tuning members are simultaneouslymoved relative to a corresponding plurality of tuned members, propertracking among the tuned members as the System is tuned from one end ofits range to the other requires that the positions of the tuning membersrelative to the moving part on which they are mounted be adjustable fromunit to unit. Slight variations in the physical or electricalcharacteristics of the mounting structure, the tuned members and thetuning members make this type of adjustment inevitable and ine-scapable.

One common type of tuned element is a helical inductance wound about acoil form. The tuning member associated therewith generally constitutesa member telescopically into or over the helically wound coil; in oneconventional form it comprises a core formed of ferromagnetic materialwhich slides inside the tubular form on which the coil is wound. Whentuning with devices of this type a further problem is presented, that ofalignment of the coil form with its corresponding telescoping member. Itis desirable that the telescoping cores be fairly snugly received withinthe coil forms, and it is essential that they be freely slidable todifferent tuning positions. Means must be provided to compensate forslight misalignments of core and coil form if effective tuning is toresult.

Various proposals have been made to provide for individual adjustabilityof the cores relative to the part on which they are mounted. Theygenerally involve the attachment to the core of a connecting member,usually rod-like in form, which extends through an aperture in themounting part, and structure is provided to permit axial adjustment ofthat element as it passes through the aperture. To compensate for slightaxial misalignments of the tuning core and its corresponding coil formit has been proposed that the connecting member be resiliently flexible,and to that end it is often defined by a helically wound metallic wirethe adjacent turns of which are preferably in contact with one another,thereby fixing its normal length, the wound wire rod being resilientlybendable along its length.

In the past the structure which has provided for adjustable mounting ofthese flexible connecting rods as they pass through the aperturel in themounting parthas added significantly to the cost of the tuner. Suchstructure either involves the use of parts other than the mounting partand the connecting rod (such as setscrews, locking nuts or resilientinserts adapted to grip the connecting rod) or the carying out of timeconsuming fabrication operations (such as the internal threading of theinner surface of the aperture and the formation and threading ofapertures for the setscrews), or both.

It is the prime object of the present invention to provide a mountingfor rod-supported tuning members which not only provides for readyindividual adjustability of high degree of security of retention of suchtuning members in their adjusted position, but which also is theultimate in simplicity and adds virtually nothing to the cost of theunit.

The commercial significance of cost in units of the type underdiscussion cannot be over-emphasized. The manufacture of tuners is anextremely competitive business. Tuners are used by radio setmanufacturers in extremely large numbers, and a difference of a fractionof a cent in the cost of manufacture of a tuner often makes thedifference between making and losing a sale for hundreds of thousands ofsuch tuners. Consequently anything which saves even a small amount ofmoney in manufacturing cost is of prime importance. The commercialsituation is, of course, greatly complicated by the equal emphasis onquality and reliability. It is not enough that a tuner be less expensivethan -a competitive item; it must also function at least as accuratelyand reliably as the competitive item. The significant fact about theconstruction here diS- closed and claimed is that it signally satisfiesboth the requirement of lack of expense and the requirement ofreliability.

In accordance with the present invention the mounting part is providedwith an aperture, and the connecting rod between the tuning member andthe movable part on which it is mounted is resiliently flexible and isprovided on its external surface with a thread. Most conveniently it maybe formed of helically wound relatively stiffiy resilient wire, such ashas been used in the past. However, the present invention departs fromthe prior art in that the aperture in the mounting part need not beprovided with a threaded inner surface; thus it need only be drilled orotherwise formed, but it does not need to be tapped, thus eliminating amanufacturing operation and therefore reducing cost. The externallythreaded connecting rod passes freely, but preferably not loosely,through this aperture. The mounting part is further provided with aninterference element which is rearwardly spaced from and at leastpartially overlaps the rear end of the aperture. This element has asurface which engages and dcects that end of the connecting rod whichhas passed through the aperture, thus forcing the opposite surface ofthe connecting rod against an edge of the aperture, one or the other orboth of said element surface and said aperture edge thereforefunctioning as a screw thread which cooperates with the external threadon the connecting rod. This permits accurate adjustment of the positionof the tuning member relative to the part through rotation of theconnecting rod, just as though the aperture in the mounting part hadbeen internally threaded. Moreover, the force exerted by theinterference element on the connecting rod where those two parts engage,as well as the force exerted on the connecting rod by the aperture edgeagainst which it is pushed by the interference element, act tofriction-ally retain the connecting rod in its adjusted position, thusreliably ensuring that the tuning member will stay where it belongs.These results, it will be noted, are achieved by means of a structurewhich may be molded or cast in one piece, thus not only reducingmaterial cost, but also greatly reducing assembly cost.

To the accomplishment of the above, and to such other objects as mayhereinafter appear, the present invention relates to a means formounting a tuning member on a movable part, as defined in the appendedclaims and as described in this specification, taken together with theaccompanying drawings in which:

the tuning members relative to the mounting part and a v FIG. 1 is afront elevational view, partially schematic, of a tuner in which thepresent invention is embodied;

FIG. 2 is a cross sectional view on an enlarged scale, taken along theline 2-2 of FIG. l; and

FIG. 3 is a fragmentary end elevational View of the mounting part alone,taken from the left-hand end of FIG. 2.

FIG. 1 discloses, more or less schematically, a tuner comprising achassis support 2 on which are mounted a plurality of tuned membersgenerally designated 4, each of these tuned members in the form herespecifically disclosed comprising a tubular coil form 6 mounted on thechassis supportZ, that coil form having a tuning coil S wound over theexterior thereof, the coil form 6 having a hollow interior 1f).Associated with each tuned member 4 is a tuning member generallydesignated 12 here disclosed, as is conventional, in the form of a core14 formed of ferromagnetic material which is adapted to be relativelysnugly telescopical slidably received within the hollow interior 10 ofits associated coil form 6. As will be apparent, the degree to which thecore 14 is telescoped within the coil form 6 will cause the inductanceof the coil S to vary, thus producing a tuning effect.

A movable mounting part generally designated 16 is here shown in theform of a structural element having a cross bar 18 which is adapted tobe moved toward and away from the upper ends of the coil forms 6. Thepart 16 is mounted in any appropriate manner in the tuner and is movedtoward and away from the upper ends of the coil form 6 by anyappropriate mechanism in order to simultaneously tune all of the tunedmembers 4. The cores 14 defining the tuning members 12 are therefore allconnected to the cross bar 18, that connection being accomplished byconnecting rods generally designated 20 which are liexibly resilient andwhich have an outer surface which defines an external threadedconfiguration. 1n the form here specifically disclosed the connectingrods 20 are defined by tension springs formed of closely helically woundresilient metal wire, the external threaded configuration of theconnecting rods being defined by the radially outwardly disposedsurfaces of the wire turns. Preferably, but not necessarily, the turnsof the helices axially engage one another so that the normal length ofthe thus-defined connecting rods 20 is fixed. One end of each rod 20 issecured to a tuning core 14, as by being embedded therein, as at 26; theother ends of the rods 20 are free.

The cross bar 18 on the movable mounting part provided with anupstanding wall 22 having a series of apertures 24 therethrough, theapertures 24 being aligned with the open ends of the coil forms 6 andbeing of approximately the same size as the maximum external diameter ofthe connecting rods 20, so that the connecting rods. 20 can berelatively snugly received within the apertures 24, while at the sametime being more or less freely axially movable therethrough. It is afeature of the present invention that the internal surface of theapertures 24 need not be threaded, although threads may be thereprovided if desired. The structure of the present invention willfunction in an entirely satisfactory manner even with a smooth sidedaperture 24, as is here specifically disclosed.

Each aperture 24 has a front end which faces the corresponding coil form6 and a rear end defined at least in part by an upper corner edge 28.The cross bar 18 of the movable mounting part 16 also carries a seriesof interference elements which are located rearwardly spaced from therear end of the apertures 24 and which partially overlap said rearaperture ends. As here specifically disclosed interference elements 30overlap the lower portions of the rear aperture ends, at a pointdiagonally opposite from the upper corner edges 28 of the apertures 24.Side walls 32 extend rearwardly from the rear ends of the apertures 24for a short distance, the upstanding wall 22, the apertured partsthereof, the interference elements 3f) and the side walls 33 allpreferably being integrally formed to define a single easily moldedstructure, as may best be seen from FIGS. 2 and 3.

When a given tuning member 14 is to be secured to the mounting part 16the free end of its connecting rod 20 is passed through the aperture 24from the front end to the rear end thereof. When the tip of theconnecting rod 20 appears in the axial space between the rear apertureend and the interference element 30 it is lifted so as to clear theinterference element 30. This causes the resiliently fiexible connectingrod 20 to bend upwardly about the upper corner edge 28vof the aperture24, that edge 28 then engaging and cooperating with the external threadon the connecting member 20, producing in effect a threadedinterengagement between connecting rod 20 and part 16 despite the factthat the aperture 24 is not internally threaded'I-Ience the precisepositioning of each tuning member 14 relative to the part 16 may beaccurately achieved through rotation of the connecting rod 20 relativeto the part 16.

The free end of the connecting rod 20 will extend axially beyond theinterference element 30, and the resiliency of the 'connecting rod 2t)will cause its free end to engage with the upper surface, and usuallythe upper forward corner, of the element 30. This will produce a secondarea of threaded engagement between the connecting rod 20 and the part16, and it will further ensure so firm an engagement between theconnecting rod 20 and the interference element 30 and between theconnecting rod 20 and the upper corner edge 28 of the aperture 24 as toreliably frictionally retain the connecting rod 20 in any adjustedposition in which it may be placed. The side walls 32 prevent the freeend of the connecting rod 20 from moving laterally, and thus prevent itfrom escaping from the interference element 30.

When, as is here disclosed, the connecting rod 20 is formed of ahelically wound spring, the axial deformation of that rod at the uppercorner edge 28 of the aperture 24 and at the active surface of theinterference element 30 will tend to cause adjacent turns o-f thehelical coil to separate, thus producing a vvery firm and positivethreaded interengagement between the appropriate surfaces of themounting part 16 and the corresponding areas of the connecting -rod 20,thus enhancing the degree of security provided against accidentalVshifting of position.

It is noteworthy that in the products of the present invention notapping operations need be performed, no

`extra parts need be made or purchased, assembly operations are entirelyeliminated, and thus cost is greatly minimized, but without anysignificant sacrifice in ease of adjustment of the positions ofindividual tuning members 12 or the security of that adjustment whenonce made.

While but a single embodiment of the present invention has been herespecifically disclosed it will be apparent that many variations may bemade therein, all within the scope of the instant invention as definedin the following claims.

I claim:

1. In a tuner comprising a support, a tuned member mounted thereon, atuning member movable relative to said tuned member to tune the latter,a part operatively connected to said support and movable relativethereto, and means connecting said tuning member to said part formovement therewith', the improvement which cornprises said part havingan aperture with front and rear ends respectively operatively facingtoward and away from said tuning member, an element on said partrearwardly spaced from and at least partially overlapping said rear endof said aperture, and said connecting means comprising a resilientmember the outer surface of which defines an external threadedconfiguration, said resilient member passing through said aperture andengaging and being deflected by said element.

2. The tuner of claim 1, in which the maximum external diameter of saidresilient member is not appreciably greater than the internal diameterof said aperture.

3. The tuner of claim 2, in which an edge of said element engages saidresilient member between adjacent external threads thereon.

d. The tuner of claim 2, in which an edge ot said element and an edgeor" said rear end of said aperture engage said resilient member betweenadjacent external threads thereon.

5, The tuner of claim 2, in which the resilient-memberengaging Surfaceof said element is concave, said member being received within saidconcavity.

6. The tuner of claim 2, in which an edge of said element engages saidresilient member between adjacent external threads thereon, and in whichsaid edge of said element is concave, said member being received withinsaid concavity.

7. The tuner 01' claim 2, in which an edge of said element and an edgeof said rear end of said aperture engage said resilient member betweenadjacent external threads thereon, and in which said edge of saidelement is concave, said member being received within said concavity.

8. The tuner of claim in which the maximum eX- ternal diameter of saidresilient member is not appreciably greater than the internal diameterof said aperture, and in which said element is spaced rearwardly fromsaid rear end of said aperture by a distance greater than the diameterof said resilient member.

9. The tuner of claim 8, in which an edge of said element engages saidresilient member between adjacent external threads thereon.

1b. The tuner of claim 8, in which an edge of said element and an edgeot said rear end of said aperture engage said resilient member betweenadjacent external threads thereon.

11. rThe tuner of claim Si, in which the resilient-member-engagingsurface of said element is concave, said member being received withinsaid concavity.

12. The tuner of claim S, in which an edge of said element engages saidresilient member between adjacent external threads thereon, and in whichsaid edge of said element is concave, said member being received withinsaid concavity.

13. The tuner or" claim 3, in which an edge of said element and an endof said rear end of said aperture engage said resilient member betweenadjacent external threads thereon, and in which said edge of saidelement is concave, said member being received Within said concavity.

14. The tuner or" claim 1, in which an edge of said element engages saidresilient member between adjacent external threads thereon.

15. The tuner of claim 14, in which the resilient-member-engagingsurface of said element is concave, said member being received withinsaid concavity.

16. The tuner of claim 1, in which an edge of said element and an edgeof said rear end of said aperture engage said resilient member betweenadjacent external threads thereon.

17. The tuner of claim 16, in which the resilient-member-engagingsurface of said element is concave, said member being received withinsaid concavity.

1%. The tuner of claim 1, in which the resilient-member-engaging surfaceof said element is concave, said member being received within saidconcavity.

19. The tuner of claim 1, in which said resilient member comprises ahelicaily wound resilient length, adjacent turns of which deline saidexternal threaded configuration.

Reierences Cited UNITED STATES PATENTS Aug. 18, 1960.

LARAMIE E. ASKIN, Primary Examiner. T. I. KOZMA, Assistant Examiner.

1. IN A TUNER COMPRISING A SUPPORT, A TUNED MEMBER MOUNTED THEREON, ATUNING MEMBER MOVABLE RELATIVE TO SAID TUNED MEMBER TO TUNE THE LATTER,A PART OPERATIVELY CONNECTED TO SAID SUPPORT AND MOVABLE RELATIVETHERETO, AND MEANS CONNECTING SAID TUNING MEMBER TO SAID PART FORMOVEMENT THEREWITH; THE IMPROVEMENT WHICH COMPRISES SAID PART HAVING ANAPERTURE WITH FRONT AND REAR ENDS RESPECTIVELY OPERATIVELY FACING TOWARDAND AWAY FROM SAID TUNING MEMBER, AN ELEMENT ON SAID PART REARWARDLYSPACED FROM AND AT LEAST PARTIALLY OVERLAPPING SAID REAR END OF SAIDAPERTURE, AND SAID CONNECTING MEANS